Probably Polarity


I need your assistance with my boat wiring.

I have changed trolling motor batteries in my boat and since, I have burned 2 twist plugs. My cables aren’t marked so is it possible I may have crossed them or is that something that would cause my dilemma.

What could be causing me to burn the plug? It has a 4 wire Marinco outlet.

Thank you


On a 12/24 marine electrical system, wiring the batteries is critical. Use a meter (not a test light) to determine if the polarity is correct and the battery cables are correctly connected.

The circuit protection in the positive leads at the battery should trip before you burn up the plug. If you don’t have fuses or breakers at the battery, now is a great time to add them.


Series Jumper OK


I have a 24v trolling motor. My boat battery wiring consists of two 12v agm, wired in series and the unit is served via a twist plug/receptacle setup. The unit is protected by a 60 amp fuse.

To avoid climbing into the boat to hook up a charger, I installed a Guest 2611 10amp battery charger capable of charging two batteries at the same time. This is wired to each battery via two cables having a positive and negative lead with the positive fused. The unit is powered via 110v AC.

I ran with this setup last season and even charged the system a few times – or thought I did. I was rewiring the batteries due to a corrosion problem when I realized  that while having the charger wired correctly to their respective terminals, I have a wire that goes from positive to negative connecting the battery in series.

These terminals have a positive and negative wire respectively attached to them from the charger. I’m wondering if the charger is functioning at all?

Guest markets the unit as having numerous safety features, perhaps these features have saved me from ruining an expensive unit that has  been incorrectly wired from the beginning.

What’s your opinion?


Hi Jim,

Your marine electrical has been correctly wired. I have seen hundreds of 2611 chargers installed in this manner.

The Guest 2611 has two independent chargers inside of it. External marine battery wiring, such as a series jumper, has no effect on the performance of the charger.

Hope this helps,


Rusty Minn Kota

Hi Kevin,

I have an Allison boat with a 225 Mercury Engine, Minn Kota 36 volt trolling motor, a single 12 volt crank battery and three 12 volt marine batteries wired to 36 volt for trolling.

Recently installed onboard Stealth Charger DC/AC. It allows the engine alternator to charge the crank battery and the Stealth Dc unit converts to 36V and charges the trolling batteries. The AC charger tops off boat batteries while boat is stored. All four batteries are good. Both the AC and DC charging works correctly.

Since installing the charger I have run the engine about six hours and trolling motor about fifty hours. On the first trip out, it was one hour on the engine and six hours trolling.

I noticed the trolling motor stainless steel prop nut rusted and my stainless steel engine prop corroded and the unpainted Sportmaster lower unit housing corroded. I had been on a lake I normally don’t go to. I thought it was something in the water.

Well, I just got back from four days of fishing – about five hours on engine and 44 hours trolling. The heads of the stainless steel screws that hold the transducer in the trolling motor had completely rusted off and water went in the trolling motor and the motor quit. The skeg and motor housing appear to be powder coated and the powder coat was bubbled up and white corrosion on housing and skeg.

My dealer tells me that I have a boat wiring problem and I had also probably hit a stump with trolling motor because the skeg was not vertical with trolling motor shaft.

The best that I recall the skeg was never vertical with the shaft. So I took the motor apart the 10 inch long bolts were not bent. There is a channel if bolts were installed correctly the bolts would be in the middle of the space between the motor magnets and the skeg would be vertical. The bolts were over close or against the magnets. The water ingestion and continuing to run caused the motor to fail.

My question: Is the trolling motor, charger, or boat wiring causing the extreme corrosion? I checked and all of my boat battery wiring is clean and tight.



Hi Rex,

Galvanic corrosion occurs when you have two different metal objects that are electrically connected and immersed in the same body of electrolyte. Basically, the part that is more + on a DC meter will corrode away to protect the item that is more -.

You try to keep this difference down below 0.5 volts to keep metals from corroding quickly. When you accidentally apply 12 volts (or maybe even 36 volts in your case) to one of the metal objects in this cell, it will corrode very quickly.

My best guess: 12 volts or higher was accidentally applied to the exterior metal of the trolling motor housing (motor short, transducer housing, transducer cable, trolling motor connection, etc). When the charger was installed, it completed the galvanic cell to allow the corrosion to begin.



Thanks for the quick response. Since I e-mailed you I talked to the owner of Stealth Chargers.

He said what changed when I installed the charger is we now have a common ground between the crank & trolling batteries. Prior to charger install the trolling motor + & – were independent.

The Minn Kota trolling motor assembled with the case bolts against the magnets is probably the voltage leak. Add the common ground and boom you get a floating battery that as been known to bring fish to the surface. He told me how to check it once I replace the trolling motor to make sure it was not coming from another source. I’ll let you know how it turns out.


Wrong Charger?

Hi Kevin,

I hope you can help me with a boat wiring issue.

On my boat battery wiring, I have two batteries for my trolling motor, a 24 volt Motorguide. They are hooked up

  • + to motor
  • – on battery to + on 2nd battery
  • – to trolling motor

The on board marine electrical battery charger has connections for two batteries. Do I just hook it up positive and negative on both batteries?

The reason I ask is the in line fuse on one battery was blown as I took it apart today.



Hi Dean,

Most dual output battery chargers are designed to be connected the way you had them.

The blown fuse may just be a fluke or your charger may not be designed to charge your batteries in series. Check with the manufacturer’s recommendations. If they say 12/24 volt systems, then you are good to go. If not, you will need to disconnect the batteries to charge or buy another charger.


Glen-L Wiring


I am building a 16′ wooden bass boat using the Glen-L design and it is about 80% complete. I am now getting ready to outfit the interior, build the helm, purchase my motor, etc.

I have visited your sister boat wiring site and it looks like just what I will need due to its simplified “plug and play ” approach. What I am looking for is advice on everything I will need to wire my boat using EzAcDc marine electrical.

My boat wiring needs include:

  • On /Off
  • Navigation lights (2 for bow red and green plus one for stern white)
  • Power winch connection for my anchor
  • Boat battery cable (2 batteries)
  • Electric trolling motor connection
  • Wiring to connect rope lighting
  • Stereo connection
  • Fish finder at bow
  • Fish finder / chart mapper on the helm
  • Connection for an electric boat horn
  • Power outlets for spot light and for plug in portable bait well pump / aerator
  • Battery switch system with wiring
  • Various gauges (voltmeter, speedometer, battery condition meter, etc.)
  • Bilge pump wiring for two pumps

In summary, I need everything and look to your recommendation to help me get what I need to fully wire my boat from the boat wiring harness to fuses, circuit breakers, switches, etc.

Thank you.


Hi Kelly,

Your boat sounds great! Thank you for your interest in the products at our sister site.

Here is the boat wiring that I would recommend.

  • Fully wired eight switch marine electrical panel. This comes with one panel mounted 12 volt receptacle and you will want to add a second remote outlet.
  • Boat wiring harness that quickly snaps together with the panel above.
  • Smart Battery Switch system for two batteries. This includes cables, ground bus, and you will want to add a couple of battery boxes.
  • Navigation lights are controlled by the nav/anc switch in your new switch panel. Wiring for split red and green lights and a single white stern light is included with the boat wiring harness. The site has a variety of Attwood LED navigation light kits that may suite your needs. All come with connectors so that they will snap right onto the new harness.
  • I would run 8 AWG tinned wire for your trolling motor.
  • Please send me the specs and length of total wire run for the power winch to determine the cable size requirements.
  • Currently we do not stock a trolling motor connection. My preference in the Marinco Connect Pro System.
  • You can use one of the switches on the new panel for the stereo. The new panel will even include a pre-printed “STEREO” switch cap. There is a ground, constant power (memory), and switched power coming off of the back of the switch for a stereo. We do not include speaker wire.
  • The boat wiring harness has two breakouts for courtesy lights. The switch panel kit also includes a “COURTESY LIGHTS” switch cap.
  • We do not have fish finders, but you can get power for your fish finder from one of the breakers on your new switch panel.
  • The switch panel comes pre-wired with a horn button and the boat harness includes wiring for a horn.
  • We also have boat horns that will attach easily onto the new harness.
  • We do not have gauges. Most of the gauge wiring will be included with your engine harness.
  • Our harness comes with one bilge pump and auto float switch connection. You can either run a second pump from one of the switch panel accessory wire breakouts or you can use the livewell pump breakout for a second pump.
  • No additional fuse panel is needed. The switches have circuit breakers mounted directly below them on the panel. The main harness battery connection has an in-line circuit breaker for harness protection.

Thank you again for your consideration. I hope this helps,



My boat anchor winch is the Deck Mate 19 Small Boat Anchor Windlass from West Marine. The draw is 15 amps @ 12 volts and the winch includes a built in 15A circuit breaker. The length of wire from the helm to the power winch at the bow is roughly 9 feet. Please advise cable size requirement.

Thank you.


Hi Kelly,

18′ run total @ 15 amps with 3% drop, I would run 10 AWG wire.